Malfunctions of domestic oil furnaces are a cause of frequent service calls. Such service calls must be made with some urgency since when the furnace in the home is not working there is no heat. There is a danger of pipes freezing, and even a danger to health in some cases.
Furnaces can malfunction for a variety of reasons. The ignition system for igniting the oil generally uses an ignition transformer or electronic ignitor. One such type of ignition system includes a pair of ignitor electrodes. A high tension spark is generated at the ignitor electrodes to ignite the oil. If the spark is not present, the furnace will not operate. An ignition transformer or electronic ignitor is often used to generate the high tension required for the spark. Such ignition transformers or electronic ignitors are known to fail and require replacement.
Thus on each such service call the service man will generally first of all test the spark to determine if the spark is adequate. If it is satisfactory then the transformer is working and he knows he must look elsewhere for the problem. If the spark is not present or is too weak, it is not satisfactory. He will then usually replace the transformer which generates the high tension for the spark.
Testing the output of a coil or transformer has often been done in a haphazard manner. For example, testing of a coil in the ignition circuit of an automobile, which frequently has problems caused by coil failure, was generally done by simply shorting the two high tension terminals on the coil with a screw driver. If there was a spark the coil was in order. It was not unusual for the mechanic to be injured by this test, but it was regularly done. This testing method was often used in domestic furnaces. However, in this case the coil terminals were located inside a housing in the burner. To test them the cover must first of all be removed. The high tension voltage in the furnace burner is much higher than was used in the ignition of automobiles, and the danger of shock was much greater.
The test was also inaccurate. The coil may give a spark when tested in this way, but the spark may not be sufficient to jump the electrodes in the burner. The serviceman will thus be misled by the result.
There are numerous other situations where it is required to test a coil or transformer, in cases other than a domestic furnace. In all these cases, the ability to perform a safe quick accurate test will greatly speed up the work of the technicians involved. While tests can be carried out with sophisticated devices costing considerable sums, these devices are not usually available at the location where the test is being carried out. They are not usually portable, or of sufficiently low cost that they can be supplied to every serviceman and technician in every situation.
There is a need for a simple, low cost, light weight, high tension tester, which can be part of the tool kit of every serviceman and technician, and can readily be carried about from place to place, wherever it is required.